The main emphasis of our work will be on further efforts to define the relationship between various lymphocyte cell surface markers and clinical disease states. The markers to be studied will include E- binding or sheep erythrocyte rosette formation, the immunofluorescent defined human T-cell marker as defined by rabbit antiserum prepared against human fetal thymocytes and surface Ig as well as the C3 receptor as markers for B-cells. Serial studies of various connective tissue disorders, systemic lupus, rheumatoid arthritis, and rheumatic fever will be completed and an analysis made of correlations between changes in absolute numbers as well as proportions of T and B cells.